In one form of a fluid flow control valve, a flow control element or valve member is movably positioned in a valve chamber between first and second valve positions for selectively fluidically coupling valve ports. The flow control element may be directly actuated by a solenoid operated plunger operatively associated with the flow control element. Alternatively, the flow control element may be actuated by a pilot valve which is directly actuated by a solenoid operated plunger. In either instance, the solenoid controllably positions the plunger to move either the flow control element to an actuated position or the pilot valve to an actuated position to allow movement of the valve member.
Typically, the valve chamber is provided by a two-piece valve housing of a magnetic material capable of withstanding high fluid pressure. The plunger is slidably received in a sleeve braised between the valve housing and a tube stop. To bias the plunger to a normal or an actuated position, the plunger typically includes a counterbore at either end receiving a spring biasing the plunger in a suitable direction. This type of assembly requires increased manufacturing cost. Also, misalignment can occur while braising the sleeve to the tube housing.
A typical application for a cartridge valve of the two position type is in an automobile transmission for switching clutches and the like. Typically, the clutches are single acting cylinders operated at relatively low pressure on the order of 500-600 psi, with 1,000 psi being maximum. As a plurality of valves may be necessary in such applications, economies in manufacturing are desirable to provide cost effective solutions to satisfy control requirements.
In higher pressure applications, a poppet type cartridge valve is required. With such a valve the poppet has a pilot hole and an orifice. It is necessary to catch the pilot valve in the pilot hole. As such, it must be properly guided and therefore must be concentric in the poppet bore. Also, the pilot is conventionally connected to the plunger with a pin which allows for floating of the two parts relative to one another. This further makes it more difficult to provide the required centering of the pilot valve relative to the pilot hole.
An additional problem in automotive applications results from the use of cartridge valves having magnetic housings. In an automotive transmission box, metallic chips and the like may result from gear wearout. Energization of the solenoid in proximity to a magnetic valve housing attracts the chips, causing valve sticking problems. This problem can be minimized using filters or screens in valve manifolds or the like. Here, again, additional parts and expense results.
The present invention overcomes one or more of the problems discussed above.